Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 240354
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1154 PM EDT Wed May 23 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 318 PM EDT Wed May 23 2018

High pressure over Michigan tonight and Friday will drift east over
the weekend and a south flow will send moisture northward to the
Great Lakes. If you like to sweat, you`re going to love the first
half of the weekend. Muggy conditions are expected with highs in the
mid 80s and dewpoints in the mid 60s.

There is a chance of thunderstorms too Saturday as low pressure
moves across Lower Michigan.

&&

.SHORT TERM...(This evening through Friday night)
Issued at 318 PM EDT Wed May 23 2018

Forecast concerns deal with fog chances tonight and precipitation
chances Friday night.

Latest sfc analysis shows high pressure centered over western
Michigan, which means light winds at the surface. There has beens
some convective mixing this afternoon and that has brought down some
drier air which was being reflected in sfc dewpoints in the 40s.
We`ll see dewpoints creep up tonight as the mixing wanes with sunset
and that will likely set the stage for some fog. Fog will be most
prevalent in the river valleys and other low lying areas and along
the lake shore. We`re not going with a dense fog advisory at this
point because confidence of wide spread dense fog is low. We are
quite a bit drier currently than yesterday at this time due to
mechanical mixing.

Humidity will begin to increase Thursday as south winds develop on
the back side of the departing high and dewpoints rise to the mid
50s. We`ll still see considerable sunshine, but it`ll be warmer and
a bit more humid.

Low pressure over the upper Mississippi Valley will move southeast
Friday and Friday night. It`ll drag a weak cold front with it but
the front will generally wash out as it moves across the state. The
low, though, will act as a focus for a few showers and/or storms
Friday. Friday will see temperatures a degree or two warmer than
Thursday and dewpoints near 60. It`ll definitely feel more humid.

.LONG TERM...(Saturday through Wednesday)
Issued at 318 PM EDT Wed May 23 2018

The warm weather pattern will persist for much of the holiday
weekend.  We are monitoring Monday for a possible change of airmass.
The High Res Euro over the past couple of runs has been drawing down
a backdoor cold front...with falling 925 mb temperatures through the
day.  The MOS guidance has also been lowering daytime temperatures
for Monday over the past couple of runs.  Will maintain the above
normal temperatures for Monday but not quite as warm as previously
forecasted.  Rainfall is currently expected to remain scattered
given the weak forcing pattern that we will be in.

An area of high pressure is shown to be centered over Ontario for
Tuesday.  This should support a dry east to northeast flow here in
MI.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1145 PM EDT Wed May 23 2018

Primarily VFR conditions will deteriorate a bit to mainly MVFR
during the early morning hours Thursday due to development of
patchy fog. Fog will likely become denser at KMKG where conditions
will deteriorate to IFR prior to daybreak.

Patchy early morning fog will gradually dissipate during the mid
morning hours and conditions at all the terminals will improve to
VFR by mid to late morning. Conditions will then remain VFR
Thursday afternoon through Thursday evening with wind speeds aob
10 kts.

&&

.MARINE...
Issued at 318 PM EDT Wed May 23 2018

The marine fog advisory remains in effect through Thursday morning.
Latest vis loop shows fog hugging the coast line. Higher dewpoints
over colder water coupled with weak winds aloft are usually a recipe
for dense fog. Otherwise, wind and waves will not be hazardous to
small craft.


&&

.HYDROLOGY...
Issued at 318 PM EDT Wed May 23 2018

Rivers will continue to fall slowly for the next couple of days.
Significant rainfall is not expected.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Dense Fog Advisory until 11 AM EDT Thursday for LMZ844>849.

&&

$$

SYNOPSIS...04
SHORT TERM...04
LONG TERM...MJS
AVIATION...Laurens
HYDROLOGY...04
MARINE...04


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